Smoke can be thought of as a combo as it is the product of the combustion(fire) of a fuel(earth). Gravity has ZERO to do with photonic activity. Shadow can't be an application of darkness alone, because you can't have a shadow without light, proving it IS a combo of light and dark.
Too be honest, except for your Earth, fire, water, air (wind), light and darkness, the others are retarded. (ice, thunder, smoke) I was only trying to help, but if you are just going to tool my suggestions, I'll remind you that lightning is the electrical component and thunder the acoustical effect of lightning, so thunder as solely a noise, is the most ridiculous, and if your story is as bad as that concept, it will fail as badly as Nazi love stories would.